IL2,Beton flugzeug.

The Il-2 (Ilyushin Il-2 / Russia: Ил-2) is an attack aircraft developed by the Soviet Union's Ilyushin Design Bureau and operated by the Soviet Air Force.
Ilyushin made almost the front half of the Il-2's fuselage out of steel. Rather than attaching armor afterwards as in a normal aircraft, the outer panel of the aircraft itself is a monocoque and armor, and the skeleton structure, outer panel, leak-proof rubber, and armor plate can be omitted, thereby reducing weight. There is. It was possible to make such an armor plate because high-strength steel that can form a curved surface by press working was developed.
The German nickname is "Beton flugzeug".